Add bridge between ApplicativeError and ApplicativeThrow

core/src/main/scala/cats/ApplicativeError.scala

@@ -21,7 +21,12 @@
 
 package cats
 
-import cats.ApplicativeError.CatchOnlyPartiallyApplied
+import cats.ApplicativeError.{
+  CatchOnlyAsPartiallyApplied,
+  CatchOnlyAsUnsafePartiallyApplied,
+  CatchOnlyPartiallyApplied,
+  CatchOnlySafePartiallyApplied
+}
 import cats.data.{EitherT, Validated}
 import cats.data.Validated.{Invalid, Valid}
 
@@ -264,6 +269,8 @@ trait ApplicativeError[F[_], E] extends Applicative[F] {
   /**
    * Often E is Throwable. Here we try to call pure or catch
    * and raise.
+   *
+   * Note: fatal exceptions (as defined by `scala.util.control.NonFatal`) will be propagated
    */
   def catchNonFatal[A](a: => A)(implicit ev: Throwable <:< E): F[A] =
     try pure(a)
@@ -274,6 +281,8 @@ trait ApplicativeError[F[_], E] extends Applicative[F] {
   /**
    * Often E is Throwable. Here we try to call pure or catch
    * and raise
+   *
+   * Note: fatal exceptions (as defined by `scala.util.control.NonFatal`) will be propagated
    */
   def catchNonFatalEval[A](a: Eval[A])(implicit ev: Throwable <:< E): F[A] =
     try pure(a.value)
@@ -282,11 +291,85 @@ trait ApplicativeError[F[_], E] extends Applicative[F] {
     }
 
   /**
-   * Evaluates the specified block, catching exceptions of the specified type. Uncaught exceptions are propagated.
+   * Evaluates the specified block, catching exceptions of the specified type.
+   *
+   * This method is considered unsafe because uncaught exceptions are propagated
+   * outside of `F`. While the name does not currently reflect this, this may change
+   * at a future date.
    */
   def catchOnly[T >: Null <: Throwable]: CatchOnlyPartiallyApplied[T, F, E] =
     new CatchOnlyPartiallyApplied[T, F, E](this)
 
+  /**
+   * Evaluates the specified block, catching exceptions of the specified type.
+   *
+   * Exceptions of type `T` are raised in `F`, other non-fatal exceptions are raised in `G`
+   *
+   * Note: fatal exceptions (as defined by `scala.util.control.NonFatal`) will be propagated
+   */
+  def catchOnlySafe[G[_], T >: Null <: Throwable]: CatchOnlySafePartiallyApplied[T, G, F, E] =
+    new CatchOnlySafePartiallyApplied[T, G, F, E](this)
+
+  /**
+   * Often E can be created from Throwable. Here we try to call pure or
+   * catch, adapt into E, and raise.
+   *
+   * Exceptions that cannot be adapted to E and raised in `F` will be raised in `G`
+   *
+   * Note: fatal exceptions (as defined by `scala.util.control.NonFatal`) will be propagated
+   */
+  def catchNonFatalAs[G[_], A](adaptIfPossible: Throwable => Option[E])(a: => A)(implicit
+    G: ApplicativeThrow[G]
+  ): G[F[A]] =
+    try G.pure(pure(a))
+    catch {
+      case t if NonFatal(t) =>
+        adaptIfPossible(t).fold(G.raiseError[F[A]](t))(e => G.pure(raiseError[A](e)))
+    }
+
+  /**
+   * Often E can be created from Throwable. Here we try to call pure or
+   * catch, adapt into E, and raise.
+   *
+   * This method is considered unsafe because exceptions that cannot be
+   * adapted to E will be rethrown outside of `F`
+   *
+   * Note: fatal exceptions (as defined by `scala.util.control.NonFatal`) will be propagated
+   */
+  def catchNonFatalAsUnsafe[A](adaptIfPossible: Throwable => Option[E])(a: => A): F[A] =
+    try pure(a)
+    catch {
+      case e if NonFatal(e) => adaptIfPossible(e).map(raiseError[A]).getOrElse(throw e)
+    }
+
+  /**
+   * Evaluates the specified block, catching exceptions of the specified type.
+   *
+   * Caught exceptions are mapped to `E` and raised in `F`.
+   * Uncaught non-fatal exceptions will be raised in `G`.
+   * Fatal exceptions (as defined by `scala.util.control.NonFatal`) will be propagated
+   *
+   * Note: `catchOnlyAs` assumes that, if a specific exception type `T` is expected, there
+   * exists a mapping from `T` to `E`. If this is not the case, consider either manually
+   * rethrowing inside the mapping function, or using `catchNonFatalAs`
+   */
+  def catchOnlyAs[G[_], T >: Null <: Throwable]: CatchOnlyAsPartiallyApplied[T, G, F, E] =
+    new CatchOnlyAsPartiallyApplied[T, G, F, E](this)
+
+  /**
+   * Evaluates the specified block, catching exceptions of the specified type.
+   *
+   * Caught exceptions are mapped to `E` and raised in `F`.
+   *
+   * This method is considered unsafe because uncaught exceptions will be propagated outside of `F`
+   *
+   * Note: `catchOnlyAsUnsafe` assumes that, if a specific exception type `T` is expected, there
+   * exists a mapping from `T` to `E`. If this is not the case, consider either manually
+   * rethrowing inside the mapping function, or using `catchNonFatalAsUnsafe`
+   */
+  def catchOnlyAsUnsafe[T >: Null <: Throwable]: CatchOnlyAsUnsafePartiallyApplied[T, F, E] =
+    new CatchOnlyAsUnsafePartiallyApplied[T, F, E](this)
+
   /**
    * If the error type is Throwable, we can convert from a scala.util.Try
    */
@@ -383,6 +466,39 @@ object ApplicativeError {
       }
   }
 
+  final private[cats] class CatchOnlySafePartiallyApplied[T, G[_], F[_], E](private val F: ApplicativeError[F, E])
+      extends AnyVal {
+    def apply[A](
+      f: => A
+    )(implicit CT: ClassTag[T], NT: NotNull[T], ev: Throwable <:< E, G: ApplicativeThrow[G]): G[F[A]] =
+      try G.pure(F.pure(f))
+      catch {
+        case t if CT.runtimeClass.isInstance(t) => G.pure(F.raiseError(t))
+        case t if NonFatal(t)                   => G.raiseError(t)
+      }
+  }
+
+  final private[cats] class CatchOnlyAsPartiallyApplied[T >: Null <: Throwable, G[_], F[_], E](
+    private val F: ApplicativeError[F, E]
+  ) extends AnyVal {
+    def apply[A](adapt: T => E)(f: => A)(implicit CT: ClassTag[T], NT: NotNull[T], G: ApplicativeThrow[G]): G[F[A]] =
+      try G.pure(F.pure(f))
+      catch {
+        case CT(t)            => G.pure(F.raiseError(adapt(t)))
+        case t if NonFatal(t) => G.raiseError[F[A]](t)
+      }
+  }
+
+  final private[cats] class CatchOnlyAsUnsafePartiallyApplied[T >: Null <: Throwable, F[_], E](
+    private val F: ApplicativeError[F, E]
+  ) extends AnyVal {
+    def apply[A](adapt: T => E)(f: => A)(implicit CT: ClassTag[T], NT: NotNull[T]): F[A] =
+      try F.pure(f)
+      catch {
+        case CT(t) => F.raiseError(adapt(t))
+      }
+  }
+
   /**
    * lift from scala.Option[A] to a F[A]
    *

tests/shared/src/test/scala/cats/tests/EitherSuite.scala

@@ -23,6 +23,7 @@ package cats.tests
 
 import cats._
 import cats.data.{EitherT, NonEmptyChain, NonEmptyList, NonEmptySet, NonEmptyVector, Validated}
+import cats.syntax.option._
 import cats.syntax.bifunctor._
 import cats.kernel.laws.discipline.{EqTests, MonoidTests, OrderTests, PartialOrderTests, SemigroupTests}
 import cats.laws.discipline._
@@ -136,6 +137,63 @@ class EitherSuite extends CatsSuite {
     assert(Either.catchNonFatal(throw new Throwable("blargh")).isLeft)
   }
 
+  test("ApplicativeError instance catchNonFatalAs maps exceptions to E") {
+    val res =
+      ApplicativeError[Either[String, *], String]
+        .catchNonFatalAs[Either[Throwable, *], Int](_.getMessage.some)("foo".toInt)
+        .leftMap(0 -> _.getMessage)
+    assert(res === Right(Left("For input string: \"foo\"")))
+  }
+
+  test("ApplicativeError instance catchNonFatalAs raises unmappable exceptions in G") {
+    val res =
+      ApplicativeError[Either[String, *], String]
+        .catchNonFatalAs[Either[Throwable, *], Int](_ => none[String])("foo".toInt)
+        .leftMap(0 -> _.getMessage)
+    assert(res === Left(0 -> "For input string: \"foo\""))
+  }
+
+  test("ApplicativeError instance catchNonFatalAsUnsafe maps exceptions to E") {
+    val res = ApplicativeError[Either[String, *], String].catchNonFatalAsUnsafe(_.getMessage.some)("foo".toInt)
+    assert(res === Left("For input string: \"foo\""))
+  }
+
+  test("ApplicativeError instance catchNonFatalAsUnsafe rethrows unmappable exceptions") {
+    val _ = intercept[NumberFormatException] {
+      ApplicativeError[Either[String, *], String].catchNonFatalAsUnsafe(_ => none[String])("foo".toInt)
+    }
+  }
+
+  test("ApplicativeError instance catchOnlyAs maps exceptions of the specified type to E") {
+    val res =
+      ApplicativeError[Either[String, *], String]
+        .catchOnlyAs[Either[Throwable, *], NumberFormatException](_.getMessage)("foo".toInt)
+        .leftMap(0 -> _.getMessage)
+    assert(res === Right(Left("For input string: \"foo\"")))
+  }
+
+  test("ApplicativeError instance catchOnlyAs raises non-matching exceptions in G") {
+    val res =
+      ApplicativeError[Either[String, *], String]
+        .catchOnlyAs[Either[Throwable, *], IndexOutOfBoundsException](_.getMessage)("foo".toInt)
+        .leftMap(0 -> _.getMessage)
+    assert(res === Left(0 -> "For input string: \"foo\""))
+  }
+
+  test("ApplicativeError instance catchOnlyAsUnsafe maps exceptions of the specified type to E") {
+    val res =
+      ApplicativeError[Either[String, *], String]
+        .catchOnlyAsUnsafe[NumberFormatException](_.getMessage)("foo".toInt)
+    assert(res === Left("For input string: \"foo\""))
+  }
+
+  test("ApplicativeError instance catchOnlyAsUnsafe propagates non-matching exceptions") {
+    val _ = intercept[NumberFormatException] {
+      ApplicativeError[Either[String, *], String]
+        .catchOnlyAsUnsafe[IndexOutOfBoundsException](_.getMessage)("foo".toInt)
+    }
+  }
+
   test("fromTry is left for failed Try") {
     forAll { (t: Try[Int]) =>
       assert(t.isFailure === (Either.fromTry(t).isLeft))

tests/shared/src/test/scala/cats/tests/TrySuite.scala

@@ -103,6 +103,20 @@ class TrySuite extends CatsSuite {
     }
   }
 
+  test("catchOnlySafe works") {
+    forAll { (e: Either[String, Int]) =>
+      val str = e.fold(identity, _.toString)
+      val res = MonadThrow[Try].catchOnlySafe[Try, NumberFormatException](str.toInt)
+      // the above should never raise an exception in the outer try
+      assertEquals(res.toEither.map(_.isSuccess), Right(e.isRight), clue(res))
+    }
+  }
+
+  test("catchOnlySafe only raise the specified type in Try") {
+    val res = MonadThrow[Try].catchOnlySafe[Try, UnsupportedOperationException]("str".toInt)
+    assert(res.isFailure, clue(res))
+  }
+
   test("fromTry works") {
     forAll { (t: Try[Int]) =>
       assert((MonadThrow[Try].fromTry(t)) === t)